1. Field of the Invention
The invention relates to a fastener for securing rigid insulation panels in place and, more particularly, to a corner fastener for securing the corners of adjacent rigid insulation boards without puncturing the rigid insulation boards.
2. Description of the Prior Art
Rigid board-type insulation, utilized under roofing has been secured in place to the underyling surface or substrate by many methods. The vast majority, approximately 99% are secured by one of three methods outlined in the following summary.
On sloped roofs, usually having a slop of over 3 inches per foot, nails with either common or with large flat heads are randomly spaced and driven through the insulation into the substrate. This method is used when the succeeding roof cover application requires additional nailing. This additional nailing penetrates the roofing, plus the insulation, down into the substrate providing additional means of securement. The preceding is not the case as the roof decreases in slope towards horizontal. Most low or no-slope commercial and industrial roofing membrane coverings do not permit through nailing. The most important reason for omitting nailing is, low slope construction invites ponding, forming a head of water against the nail penetrations which are not waterproofed and therefore causes leaks into the structure.
A second method to secure insulation to the substrate is by mopping, pouring or brushing various types and quantities of adhesives. Some adhesives are expensive and some are short-lived due to age-dry or hardening. Some fail because of their solubility in the presence of water. The coefficient of adhesiveness fluctuates and strong winds cause separation of the insulation from the substrate, thereby creating problems associated with wind damage or loss of roofing.
For some years major Insurance Underwriters and Building Code Officials have specifically warned about wind-uplift forces that cause delamination of insulation from the substrate. To satisfy the concern relating to wind damage losses, another or third method of securement was devised which included small discs of various size and material. The disc was provided with a small hole in the center which received a pull-down screw. The discs were placed on top of and in the field of the insulation, usually spaced six inches in from the perimeter edges. Dimensions of the insulation board, either two by four feet or three by four feet, etc. and the geographical area (tornado or hurricane), determined the quantity of discs required for installing the insulation.
In addition to the wind uplift problem there is another problematic characteristic of insulation; a shrinkage phenomena. The shrinkage is particulary prevalent in the expanded thermoplastic foam types. This shrinkage phenomena is most notable under roof applications where, hundreds of adjacent insulation boards have contracted or shifted, in mass, away from the building parapets or eave edges. This longituinal movement, sometimes over one inch fatigues or over stresses the membrane roof covering to the point of fracture which causes a serious roof leak and resultant damages.